var a:array[1..16,1..16]of longint;
    i,j,n,m,k:integer;s:longint;f,g:text;
begin
assign(f,'flip.in');reset(f);
assign(g,'flip.out');rewrite(g);
read(f,n,m);s:=0;
for i:=1 to n do
for j:=1 to m do read(f,a[i,j]);
for i:=1 to n do begin k:=0;
for j:=1 to m do
if a[i,j]<0 then k:=k+1;
if k>n div 2 then for j:=1 to m do a[i,j]:=a[i,j]*(-1);end;
for j:=1 to m do begin k:=0;
for i:=1 to n do
if a[j,i]<0 then k:=k+1;
if k>n div 2 then for i:=1 to n do a[i,j]:=a[i,j]*(-1);end;
for i:=1 to n do
for j:=1 to m do s:=s+a[i,j];
write(g,s);close(f);close(g);end.